Sleipner gas field

At the Sleipner gas field in the North Sea off Norway, natural gas is produced containing about 10 percent C02. The C02 concentration exceeds the concentration allowed in the European natural gas grid by about a factor of 4. Normally in such cases, C02 is stripped from the gas onshore and vented to the atmosphere. Since 1996, motivated by a carbon tax of about 140/t C (in U.S. dollars), the field operators are stripping C02 offshore and injecting it into the nearby Utsira formation, a very large saline aquifer that does not contain hydrocarbons. 

One option is CO2 disposal (disposal in ocean, injection in aquifers, confination in depleted gas or oil wells, injection for enhanced oil recovery). This is now done in Norway (Sleipner gas field) where 2740 t of CO2 per day are removed from natural gas. This CO2 is then compressed and injected into a water-filled sandstone reservoir (deep aquifer) [2]. 

Schematic of storage of carbon dioxide at the Sleipner gas field. (Courtesy of Intergovernmental Panel on Climate Change).

The world s first industrial-scale CO2 storage was at Norway s Sleipner gas field in the North Sea, where about one million tons per year of compressed liquid CO2 separated from methane is injected into a deep reservoir (saline aquifer) about a kilometer below the sea bed and remains safely in place. The natural gas contains 9% CO2 which must be reduced before sale or export. The overall Utsira sandstone formation there, about 1 km below the sea bed, is said to be capable of storing 600 billion tons of CO2. 

CO2 may be able to be sequestered in geological formations, such as active and depleted oil and gas reservoirs, coalbeds, and deep saline aquifers. Such formations are widespread and have the potential to sequester large amounts of CO2 (Herzog et al., 2000). A model project is underway in the North Sea off the coast of Norway. The Sleipner offshore oil and natural gas field contains a gas mixture of natural gas and CO2 (9%). Because the Norwegian government taxes emissions of CO2... 

The separation of CO2 from gas streams is reasonably well known. The most obvious example is its removal from natural gas. In some cases, the amounts may be quite large some economically recoverable natural gas reservoirs contain significant amounts of carbon dioxide. The Sleipner West field in the North Sea (for example) contains 10% by volume CO2 the sales specification is not more than 2.5%. Statoil (the Norwegian state oil company), which operates the field, uses an anune solvent technique to separate the excess, which is then pumped into a reservoir 1 km below the seabed. Approximately 1 million tonnes of CO2 is separated annually, which is about 40% of the model Kenosha plant described above. 

Norway, with a tax as high as 54.00/t of C02, is currently gaining attention for its massive sequestration project, the sole purpose of which is to avoid atmospheric emissions. At the Sleipner Field, Statoil of Norway separates C02 associated with natural gas production from even deeper geological strata at the same site. Statoil annually injects one million metric tons of C02 into a capped geological formation 1000 meters below a shallow sea inlet. To provide a basis for comparison, this is approximately the C02 output from a 120-MW electric coal-fired power plant. 

Like in the Sleipner field (North Sea), the CO2 is anticipated to be captnred and stored appropriately. Additional CO2 capture is possible in the power and other energy intensive sectors. Specific possibilities for the mitigation of CO2 emissions include decarbonization of blast furnace gas in the iron and steel industry, and in the hydrogen production. 

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